KR101967963B1 - Covalent organic framework for adsorbing so2 gas and method for preparing the same - Google Patents

Abstract

The invention is already have a de backbone suitable covalent organic skeleton structure (Covalent Organic Framework, COF), and as it relates to a process for the manufacture, covalent organic skeleton structure according to the invention as an adsorbent of SO ₂ gas, and SO ₂ It is the porosity of a hexagonal network structure with reactive polar groups.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a covalent organic skeleton structure for sulfur dioxide adsorbent,

The present invention is directed to a covalent organic framework (COF) suitable as an adsorbent for SO ₂ gas.

Since the SO ₂ gas generated during the coal gasification process causes serious environmental problems such as acid rain and soot, it is desirable that SO ₂ is effectively removed from the exhaust gas. Also, since the currently used desulfurization process is a low-efficiency process, efficient SO ₂ gas removal can not be performed. As a result, SO ₂ , a harmful substance, acts as a catalyst inhibitor in Selective Catalyst Reduction (SCR), thereby reducing the efficiency of the selective catalytic reduction process.

Meanwhile, a conventional coal gas desulfurization (FGD) has been developed by a method such as lime and ammonia scrubbing, physical adsorption through an organic solvent, and the like. However, such a desulfurization apparatus has a disadvantage that the SO ₂ adsorption efficiency is very low, and it generates a large amount of organic wastewater and an organic solvent. In addition to the low adsorption efficiency as described above, since the ratio of SO ₂ in the coal gas is as low as 0.2 vol%, effective removal of SO ₂ is limited only by physical adsorption.

As an alternative to such a conventional desulfurization apparatus, studies have been made on IL (Ionic Liquid) composed of a combination of a cation and an anion, but the disadvantage is that the SO ₂ adsorption rate is very slow due to the high viscosity.

Recently, researches on COF having permanent porosity and large surface area while having crystallinity in the gas storage field have been actively carried out. Adsorption studies on various gases such as N ₂ , CO ₂ and CH ₄ have been carried out, but no COF has been reported for the adsorption of SO ₂ .

The present inventors provide the must achieve physical adsorption and at the same time, SO ₂ and a charge transfer complex (charge transfer complex) to form a new adsorbent of the COF based capable of adsorbing chemically a SO ₂ gas to through the pores (pore) of the COF I want to.

The present invention relates to a covalent organic skeleton structure, which is a porous covalent organic skeleton structure having a hexagonal network structure having an imide backbone and having a functional group capable of chemical reaction with SO ₂ to provide.

The imide backbone may be one generated by the reaction of PMDA and TAPA.

The imide backbone may have the following structural formula as a repeating unit.

The polar group may be at least one selected from the group consisting of a carboxyl group and a triphenylamine group.

It is preferable that the covalent bonding organic skeleton has a BET surface area of 90 to 1,000 m < 2 > / g.

Covalent organic skeletal structure may be used as the SO ₂ sorbent for adsorbing SO ₂ in the exhaust gas.

At this time, the SO ₂ adsorbent can adsorb 0.3 to 0.45 g of SO ₂ per 1 g of the adsorbent.

The sorbent when SO ₂ absorption IR spectrum has a peak of 1323㎝ 1145㎝ ^-1 and ^-1 in combination with SO _2, SO ₂ IR spectrum after desorption has disappeared and the 1323㎝ ^-1 and 1145㎝ ^-1 peak, And may have an existing peak at 1320 cm ^-1 .

The present invention also provides a process for preparing a covalently bonded organic skeleton, comprising the steps of preparing a mixed solution by dissolving PMDA, TAPA and DMMA in a solvent, and heating the mixed solution by microwave irradiation to react PMDA and TAPA And recovering the post-precipitated reaction product, wherein the organic skeleton structure has an imide backbone, and a porous covalent organic skeleton structure having a hexagonal network structure is obtained.

Preferably, the mixed solution contains TAPA in an amount of 0.6 to 1.8 molar ratio based on 3 equivalents of PMDA and DMAR in a molar ratio of 0.6 to 4.2.

The mixed solution preferably contains DMMA in a proportion of 10 to 60 mol% based on the molar amount of TAPA.

The solvent is preferably a cosolvent comprising mesitylene, NMP and isoquinoline.

The heating can be performed by irradiating the microwave at a temperature of 200 to 250 ° C for 2 hours to 2 hours and 30 minutes.

By introducing the COF provided in the present invention into a conventional FGD process having a low efficiency, SO ₂ can be effectively adsorbed and removed.

The COF provided in the present invention is a porous material that has a very high adsorption efficiency and can be completely desorbed, and it is expected that the COF of the present invention can be efficiently applied in a future process for treating harmful gases.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a diagrammatic representation of a structure for a portion of a COF provided by the present invention.
Fig. 2 is a conceptual diagram schematically showing a mechanism by which the COF provided by the present invention adsorbs SO ₂ .
3 is a graph showing the difference in surface area according to the molar ratio of DMMA as the COF obtained in the embodiment of the present invention.
FIG. 4 is a graph showing SO ₂ adsorption amounts of respective COFs according to the molar ratio of DMMA obtained in the embodiment of the present invention, wherein (a) is for a weight unit, (b) is for SO ₂ per unit surface area N ₂ adsorption amount.
5 shows the results of IR spectrum analysis of COF according to the molar ratio of DMMA obtained in the example of the present invention, wherein (a) does not include DMMA and (b) contains DMMA in an amount of 10 mol% .
Figure 6 is a graph showing test the SO ₂ adsorbing ability reproducibility according to the adsorption and desorption of SO ₂ in the COF according to the molar ratio of DMMA obtained in the embodiment of the present invention.

The present invention aims to provide a COF (Covalent Organic Framework) suitable for SO ₂ adsorption and desorption by showing a high efficiency of SO ₂ adsorption and enabling complete desorption.

The COF provided in the present invention is an adsorbent having excellent effects in terms of recycling since it is light, flexible and environmentally friendly since all the constituent elements are organic, and can be reused after desorption. As a substitute for the existing low efficiency desulfurization apparatus It is expected to be applicable.

Accordingly, the present inventors have found that COF-based compounds capable of chemically adsorbing SO ₂ gas by achieving physical adsorption through the pores of COF and forming charge transfer complexes with SO ₂ through amine functional groups To provide an adsorbent.

The COF provided in the present invention is preferably a substance capable of easily attaching a functional group capable of interacting with SO ₂ , which is a component to be adsorbed, while simultaneously forming a channel through which the gas can effectively pass.

Accordingly, the present invention provides a COF having an imide backbone. The COF having the imide backbone provided by the present invention is thermally / chemically very stable. Therefore, even when used as an adsorbent for adsorbing SO ₂ from a high temperature exhaust gas, its porous structure can be maintained, and initial SO ₂ adsorption performance can be maintained for a long period of time even after adsorbed SO ₂ is desorbed.

The COF having the imide backbone of the present invention can be produced by the reaction of pyro-mellitic dianhydride (PMDA) with tetra (4 - [(dimethylamino) methyl] aniline). By these reactions, a basic unit structure having an imide bond of the following structure is formed.

These are repeated by polymerization to form a hexagonal structure as shown in Fig. 1, and further, by forming a network with each other, a porous COF having a hexagonal network structure as shown in Fig. 2 is formed.

This porous COF can trap SO ₂ in the pores. However, SO ₂ is the problem that this is merely physical adsorption, the adsorption loss of SO ₂ and so on out of the adsorbed SO ₂ is located within the pores of the porous COF as described above occurs. Further, since the imide backbone is provided, the heat resistance is excellent, but the structure of the network is changed due to the temperature change by repeating the adsorption and desorption processes, thereby causing the problem that the adsorption capacity is decreased.

Accordingly, the present invention intends to introduce a functional group reactive with SO ₂ into the COF. By introducing a functional group reactive with SO ₂ in this way, it is possible to physically adsorb CO ₂ by a porous structure and chemically adsorb SO ₂ by a functional group. Chemical adsorption and desorption of SO ₂ by the functional group is, for the case of introducing a dimethyl amine functional groups capable of adsorbing SO ₂ for example, can be expressed by the following mechanisms.

Thus, even if there is a change in the porous structure due to the temperature change due to the repetition of the adsorption and desorption processes, the adsorption ability can be maintained through chemical adsorption, and excellent reproducibility can be ensured. Further, SO ₂ can be prevented from escaping through chemical adsorption.

Examples of the functional group reactive with SO ₂ include dimethylamine group, guanidinium group, alkanol amine group, DABCO group and azole group. Any of these functional groups may be used alone, or two or more functional groups may be introduced at the same time.

By introducing the functional group, the surface area of COF is partially reduced by the introduced functional group. However, the reproducibility of the SO ₂ adsorbing ability by a functional group as described above may significantly increase to be more efficient as the SO ₂ sorbent.

The COF of the present invention can be carried out by dissolving PMDA, TAPA and DMMA in a solvent and irradiating microwaves.

First, the PMDA, TAPA and DMMA are dissolved in a solvent to prepare a mixed solution. In preparing the mixed solution, TAPA is preferably contained in an amount of 0.6 to 1.8 molar ratio based on 3 equivalents of PMDA, and DMAM is preferably contained in a molar ratio of 0.6 to 4.2.

At this time, the DMMA is preferably contained in an amount of 10 to 60 mol% based on the molar amount of TAPA. When DMMA is used in an amount of less than 10 mol%, there is a problem that the equivalent amount thereof is so small that COF with a functional group can not be formed. Therefore, DMMA is preferably added in an amount of 10 mol% or more.

When DMMA is added, the π-π interaction between PMDA and PATA, which are two building blocks composing the COF, is decreased and the amorphous region is increased. As a result, the porous structure is relatively broken. Is increased as the amount of DMMA added increases. As a result, the amount of SO ₂ adsorbed per 1 g of the adsorbent is reduced, but the amount of adsorbed per unit surface area is increased. However, if it exceeds 60%, the pores are clogged and the characteristic as the COF is damaged.

More preferably, the DMMA is used in a molar ratio of 3 equivalents to TAPA in the range of 10 to 40 mol% from the viewpoint of maintaining the pore structure of COF and the chemical adsorption capacity of SO ₂ , and most preferably 10 To 20 mol%.

The PMDA, TAPA and DMMA are dissolved in a solvent to prepare a mixed solution. As the solvent used herein, a co-solvent of mesitylene, NMP (N-methylpyrrolidone) and isoquinoline may be used. Of these, isoquinoline acts as a catalyst to convert the side-product, isoimide, to the imide in the imide reaction. The solvent preferably contains NMP in a volume ratio of 0.8 to 1.2 based on the volume of mesitylene. The isoquinoline may be contained in a volume ratio of 0.1 to 0.5 based on the volume of mesitylene.

The mixed solution is irradiated with microwave and heated to react the PMDA, TAPA and DMMA. In the present invention, irradiation of microwaves is preferable because the reaction time can be remarkably shortened.

At this time, it is preferable that the temperature of the mixed solution is heated to 200 to 250 ° C by irradiating microwave. There is a problem that the yield of the product is low. Although the reaction can be carried out at a temperature of 250 ° C or higher, there is no special effect due to the rise of the temperature, and the pressure may be increased, resulting in a load on the equipment.

Further, the microwave is preferably irradiated for 2 hours to 2 hours and 30 minutes to maintain the temperature range. If it is outside the above range, there is a problem in forming a crystalline skeleton.

The brown precipitate is formed by such a reaction. The precipitate is separated by filtration, washed and dried to obtain the COF of the present invention.

The COF obtained by the present invention can be suitably used as an SO ₂ adsorbent. The COF of the present invention can adsorb 0.45 g, for example, 0.3 to 0.45 g of SO ₂ per 1 g of the maximum COF, and can exhibit a very excellent SO ₂ adsorption efficiency. Such an excellent adsorptivity is exhibited because it has a high surface area due to the porous structure and contains functional groups capable of chemically adsorbing SO ₂ .

The COF provided by the present invention is different depending on the introduction amount of DMMA, but has a BET specific surface area value of about 90 to 1,000 m 2 / g. And due to the functional groups introduced by DMMA as described above, if having a specific surface area value of the above range can increase the chemical SO ₂ adsorption amount, and it is possible to maintain the porous structure of COF, for optimal SO ₂ adsorbing ability have. More preferably 500 to 900 m < 2 > / g.

Thus COF of the present invention is that the functional groups react with SO ₂ being introduced into a polar functional group having reactivity with respect to SO _2. Therefore, it is possible to determine whether the chemical adsorption of SO ₂ by comparing the COF of adsorption before and after the SO _2. For example, in the IR spectrum analysis, when a functional group is chemically adsorbed with SO ₂ , a peak that was not present before adsorption can be observed. That is, when the dimethylamine group adsorbs SO ₂ , it has peaks at 1323 cm ^-1 and 1145 cm ^-1 . The IR spectrum after SO ₂ desorption disappears at the peaks at 1323 cm ^-1 and 1145 cm ^-1 , Lt; ^-1 > cm < ^-1 >

Example

Hereinafter, the present invention will be described more specifically by way of examples. The following examples are merely illustrative of the present invention and should not be construed as limiting the present invention.

Comparative Example  One

To a solution of mesitylene (3 ml) / NMP (3 ml) / isoquinoline (0.3 ml) in a glove box under N ₂ atmosphere was treated with PMDA (615 mg, 0.76 mmol) and TAPA (140 mg, 0.48 mmol) To prepare a mixed solution.

The mixed solution was sealed in a 10 ml glass microwave tube under nitrogen and then irradiated with microwaves at 300 W for 2 hours using an Anton Paar microwave synthesizer (MonoWave 300) and heated to 200 ° C. The resulting brown precipitate was separated and recovered by filtration with 100 ml of purified THF.

The product was immersed in 100 ml of THF for 8 hours while changing the activation solvent four times. The solvent was removed under vacuum at 100 캜 to obtain PI-COF-m (the product obtained through the microwave synthesis method) as a brown powder. The analysis results for C ₆₆ H ₃₀ O ₁₂ N ₈ are as follows.

Calculated: C, 84.8; H, 0.32; N, 12.0.

Found: C, 83.3; H, 0.48; N, 11.6.

FT-IR: 1373, 1505, 1720, 3045 cm ^-1

Synthetic example  One

N, N -Dimethyl-l- (4-nitrophenyl) methanamine (b)  synthesis

25 ml of excess compound dimethylamine was added to a solution of 5 g (23.1 mmol) of 1- (bromomethyl) -4-nitrobenzene (compound a) in 30 ml of acetonitrile. The mixture was stirred at room temperature for 3 hours, added with 5 ml of water and extracted twice with DCM (dichloromethane, dichloromethane). The organic phase was dried over sodium sulfate, filtered and concentrated to give 3.5 g (83%) of a yellow oil compound (b).

_{1H NMR (200MHz, CDCl 3)} δ 8.20-8.14 (m, 2H), 7.52 (d, J = 8.7Hz, 2H), 3.38 (s, 2H), 2.28 (s, 6H)

Synthetic example  2

4 - ((dimethylamino) methyl )aniline( DMMA , (c))

A mixture of 3.5 g (19.4 mmol) of compound (b) in ethanol was heated to 65 < 0 > C. 0.83 g (0.39 mmol) of FeCl ₃ 6H ₂ O and 0.07 g (5.85 mmol) of activated carbon were added and 9.8 g (194 mmol) of 80% hydrazine hydrate was added dropwise at a rate to maintain a temperature below 70 ° C .

The reaction was heated at reflux for 5 hours, cooled to room temperature and then concentrated. 500 ml of water was added and the reaction solution was extracted three times with DCM.

The organic extracts were combined, dried over sodium sulfate, and concentrated to give 3.2 g (75%) of colorless cucumber compound (c).

2H), 3.30 (s, 2H), 2.21 (s, 2H), 6.30 (d, J = 8.4 Hz, 2H) , 6H)

Example  1 to 4

PI- COF - mX  synthesis

A 10 ml microwave glass tube was filled with PMDA, TAPA and DMMA as shown in Table 1 below.

Mole ratio
(PMDA: TAPA: DMMA) PMDA
(mg) TAPA
(mg) DMMA
(mg) Quantity
(mg) Average molar functionality PI-COF-m10 3: 1.8: 0.6 165 132 23 230 2.22 PI-COF-m20 3: 1.6: 1.2 165 117 46 220 2.06 PI-COF-m30 3: 1.4: 1.8 165 103 70 220 1.93 PI-COF-m40 3: 1.2: 2.4 165 88 90 200 1.82 PI-COF-m50 3: 1.0: 3.0 165 73 114 180 1.71 PI-COF-m60 3: 0.8: 3.6 165 60 137 150 1.62 PI-COF-m70 3: 0.6: 4.2 165 44 160 80 1.53

The samples were vacuum treated for 2 hours and dissolved in a solution of 3 ml of mesitylene / 3 ml of NMP / 0.3 ml of isoquinoline in a glove box under N ₂ atmosphere.

The mixed solution was sealed in a glass microwave tube under nitrogen, and the microwave was irradiated at 300 W for 2 hours at 200 DEG C using an Anton Paar micro-wave synthesizer (MonoWave 300) to generate a brown precipitate And separated by filtration with 100 ml of purified THF.

The product was precipitated in 100 ml of THF for 8 hours. Meanwhile, the active solvent was changed 4 times.

The solvent was removed under vacuum at 100 < 0 > C to yield PI-COF as a brown powder.

Surface area measurement

The specific surface area of each COF obtained in Comparative Example 1 and Examples 1 to 4 was measured by the Brunauer-Emmett-Teller (BET) method.

The measurement results are shown in Fig.

As can be seen from Fig. 3, the COF according to the present invention has a large surface area. However, as the amount of DMMA having a functional group capable of reacting with SO ₂ increases, the surface area tends to decrease.

SO2 adsorption test

SO ₂ adsorption tests were performed on the respective COFs obtained in Comparative Example 1 and Examples 1 to 4 by the SO ₂ adsorption amount measurement method based on the weighing method.

The results are shown in Fig. 4 (a) is a graph showing the weight (g) of SO ₂ absorbed per 1 g of the adsorbent, and (b) is a graph showing the number of moles of SO ₂ absorbed per m ₂ of the surface area of the adsorbent and the number of moles of N ₂ .

As can be seen from FIG. 4, when 10% by mole of the functional DMMA was added, 0.40 g of SO ₂ could be adsorbed per 1 g of the adsorbent, and as the amount of DMMA was increased, g adsorption The results are shown in Fig. As can be seen from Fig. 4 (b), when the adsorption amount per surface area is compared, it can be seen that the adsorption amount abruptly increases.

IR Study

IR spectra of the COF obtained in Comparative Example 1 and Example 1 were measured before, after, and after the SO ₂ adsorption, the once desorption, and the adsorption / desorption 5 times. The results are shown in FIG.

5 (a) is a measurement result of Comparative Example 1, and Fig. 5 (b) is a measurement result of Example 1. Fig.

As can be seen from Figure 5, Example 1 COF is 1323cm ^-1 and 1142cm as Chemical shift (chemical shift) and a new peak with chemical interaction SO ₂ adsorption when SO ₂ and dimethyl amine groups on the IR spectrum of the ^{- 1} was produced. On the other hand, in the case of Comparative Example 1, only the physical adsorption occurred due to the absence of the chemical functional group, and therefore, the IR spectrum was not changed.

These results demonstrate that the COF of Example 1 is adsorbed by chemical bonding with SO 2 by the dimethylamine group.

Further, the COF of Example 1 shows IR spectrum after desorption of SO ₂ , 1320 cm ^-1 due to the stretching of aromatic CN possessed by TAPA existing in COF before adsorption / desorption, again appears, and COF Can be reproduced.

SO2 adsorption reproducibility test

The SO ₂ adsorption and desorption cycles were repeated 5 times for COF obtained in Comparative Example 1 and Example 1, respectively, and the SO ₂ adsorption capacity in each cycle was measured.

The results are shown in Fig.

As can be seen from FIG. 6, the COF of Comparative Example 1 gradually decreased the adsorption amount of SO ₂ during five SO ₂ adsorption / desorption cycles, and the adsorption amount of 5 times was only about 75% of the initial adsorption amount.

On the other hand, the COF of Example 1 showed a constant adsorption capacity without decreasing the adsorption amount of SO ₂ during the five SO ₂ adsorption / desorption cycles, indicating that SO ₂ adsorption reproducibility was excellent.

Claims (13)

A covalent organic skeleton structure having an imide backbone and a polar group reactive with SO _2, and a polar group reactive with the SO ₂ , wherein the polar group has a hexagonal network structure of 10 to 60 mol% based on the entire structure, .
The covalently bonded organic skeleton according to claim 1, wherein the imide backbone is produced by the reaction of PMDA and TAPA.
3. The covalently bonded organic skeleton structure according to claim 2, wherein the imide backbone has the following structural formula as a repeating unit.

The covalent organic skeleton structure according to claim 1, wherein the polar group is at least one selected from the group consisting of a carboxyl group and a triphenylamine group.
The covalently bonded organic skeleton according to claim 3, wherein the BET surface area is 90 to 1,000 m 2 / g.
Any one of claims 1 to A method according to any one of claim 5 wherein the covalently linked organic skeletal structure used in the SO ₂ sorbent for adsorbing SO ₂ in the exhaust gas.
The method of claim 6, wherein the covalently linked organic skeletal structure wherein the SO ₂ sorbent to adsorb SO ₂ of 0.3 to 0.45g per 1g sorbent.
7. The method of claim 6 wherein the adsorbent during adsorption is SO ₂ IR spectrum and has a peak of 1145㎝ 1323㎝ ^{-1 -1,} IR spectrum after SO ₂ desorption of 1323㎝ ^{-1 -1} peak disappears and 1145㎝ , And a peak at 1320 cm < ^{-1 &} gt ;.
Preparing a mixed solution by dissolving PMDA, TAPA and DMMA in a solvent; And
A step of irradiating microwave to the mixed solution and heating to react PMDA and TAPA, and then recovering the precipitated reaction product
Wherein the mixed solution comprises DMMA in a molar ratio of 3 equivalents based on the molar amount of TAPA and DMMA in a proportion of 10 to 60 mol%, wherein the organic skeleton structure is imide A method for preparing a porous covalent organic skeleton structure having a backbone and having a hexagonal network structure.
10. The method according to claim 9, wherein the mixed solution contains TAPA at a molar ratio of 0.6 to 1.8, and DMMA at a molar ratio of 0.6 to 4.2, based on 3 equivalents of PMDA.
delete 10. The method of claim 9, wherein the solvent is a co-solvent comprising mesitylene, NMP and isoquinoline.
10. The method according to claim 9, wherein the heating is performed using microwaves at a temperature of 200 to 250 DEG C for 2 to 2 hours and 30 minutes.

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